Renal endometriosis mimicking an angiomyolipoma

Abstract

A 42-year-old woman, with a history of dysmenorrhea associated with low-back soreness, presented with sudden onset of right flank pain, a palpable tender mass in the right upper quadrant of the abdomen, and hematuria. A contrast-enhanced computed tomography revealed a huge encapsulated right renal tumor with a minimal fat component, which was initially diagnosed as a renal angiomyolipoma (AML) on the basis of her history and imaging findings. She underwent a right nephrectomy after initially receiving conservative treatment. Results of a pathologic examination of the resected specimen, however, revealed renal endometriosis. After the operation, she received hormone therapy with danazol. During the 10 months after the operation, no untoward events developed. Herein, we report a rare case of renal endometriosis that initially mimicked an AML.